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Chapter 1

Troubleshooting Methodology

Depending on the user, you may or may not be able to get more detailed

information. It is up to you as a network engineer or administrator to solve
the problem, which means that you may have to get the information yourself.

To be more specific, it is important that you gain as much information as

possible to actually define the problem while in the problem-definition
phase of the troubleshooting model. Without a proper and specific definition
of what the problem is, it will be much harder to isolate and resolve. Infor-
mation that is useful for defining a problem is listed in Table 1.1.

All of this information can be used to guide you to the actual problem and

to create the problem statement. Use your network diagram and go through
the checklist.

Identify Symptoms

First, you need to define what is working and what isn't. You can do this by
identifying the symptom and defining the scope. Figure 1.4 is a picture of your
network. Although the large X on the Frame Relay cloud represents that there
is an FTP connectivity issue, it does not indicate the location of the failure.
Right now, all you know is that a single user could not FTP to Host Z.

T A B L E 1 . 1

Useful Information for Defining a Problem

Information

Example

Symptoms

Can't Telnet, FTP, or get to the WWW.

Reproducibility

Is this a one-time occurrence, or does it always
happen?

Timeline

When did it start? How long did it last? How often
does it occur?

Scope

What are you able to Telnet or FTP to? Which WWW

sites can you reach, if any? Who else does this affect?

Baseline Info

Were any recent changes made to the network con-
figurations?

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